Yes, I've read through the entire thread. No, I cannot find a clear answer.

I have ~ $850 "Flight Credit" in my wallet, expiring end of March.

All of my travel since the pandemic started (it's been minimal) has been with my wife. I haven't used the flight credit on those flights, as I was told by the ExP line that the credit couldn't be used on a multi-passenger booking.

I only have one possible upcoming trip before expiration of the credit.
A) I can buy the trip as I normally would, in coach with a likely upgrade, for $300
B) I can buy that same ticket as fully refundable for $450
C) I can buy it as First Class for around $600

My questions are:
Option A, will the remainder of the Flight credit value be reissued with a new expiration date?
Option B and then cancel the refundable trip, will I receive a new flight credit with a new expiration date? For the full amount, or only for the value of this canceled flight?
If the remaining unused value is to be lost, I'll just do option C and purchase the first-class ticket

Has anyone found a good solution for extending the value of a Flight Credit? I'm sure that others must also be looking for this advice. If not... they will be once the expiration deadline nears.